Creatinine

Researched

Serum Creatinine

Kidney • Last tested 2026-01-28

What It Measures

Creatinine measures the level of creatinine in your blood, which reflects how well your kidneys are filtering waste. Since creatinine is produced at a relatively constant rate from muscle metabolism, rising blood levels indicate the kidneys are not clearing it efficiently.

Creatinine is a waste product produced by the normal breakdown of creatine phosphate in skeletal muscle. It is filtered by the kidneys and excreted in urine, making it one of the most widely used markers of kidney function. Elevated or declining levels can signal kidney disease, dehydration, or muscle-wasting conditions.

Current Value

0.9mg/dL
Reference Range: 0.71.3 mg/dL(standard)
Optimal Range: 0.81.1 mg/dL(Functional/optimal range per functional medicine guidelines. Standard lab reference: males 0.74–1.35 mg/dL, females 0.59–1.04 mg/dL (Mayo Clinic). Functional optimal: 0.8–1.1 mg/dL for both sexes, with males typically running 0.9–1.2 and females 0.7–1.0. Sources: Peter Attia MD, Chris Masterjohn PhD, Optimal DX functional ranges.)
In Range
-0.2 (-16.7%) from previous test
0.7 mg/dLOptimal: 0.81.11.3 mg/dL

What High Means

Elevated serum creatinine suggests impaired kidney filtration (reduced glomerular filtration rate). Common causes include chronic kidney disease (CKD), acute kidney injury, dehydration, excessive protein intake, rhabdomyolysis, urinary tract obstruction, and nephrotoxic medications (NSAIDs, aminoglycosides, ACE inhibitors). Very muscular individuals may have mildly elevated creatinine without kidney dysfunction.

Possible Symptoms

Often asymptomatic in early stages. As kidney function declines: fatigue, swelling in feet/ankles (edema), decreased urine output, nausea, shortness of breath, confusion, muscle cramps, itchy skin, foamy or dark urine, loss of appetite, persistent hiccups

What Low Means

Low serum creatinine can indicate reduced muscle mass (sarcopenia, cachexia, muscle-wasting diseases), inadequate protein intake, advanced liver disease (reduced creatine production), or pregnancy (increased kidney filtration). In older adults, low creatinine may mask declining kidney function due to simultaneous loss of muscle mass.

Possible Symptoms

Muscle weakness, fatigue, unintentional weight loss, difficulty with physical tasks, frailty (especially in elderly), may be asymptomatic if due to naturally lower muscle mass

Risk Factors

Chronic kidney disease, acute kidney injury, diabetes (diabetic nephropathy), hypertension, heart failure, dehydration, urinary tract obstruction, polycystic kidney disease, lupus nephritis, rhabdomyolysis, use of nephrotoxic drugs, high-protein diets (transient elevation), advanced age

Actionable Advice

Supplements

  • Astragalus
  • Alpha-lipoic acid
  • Omega-3 fatty acids
  • Coenzyme Q10
  • N-acetyl cysteine (NAC)
  • Probiotics
  • Vitamin D
  • B vitamins
  • Cordyceps

Diet & Lifestyle

  • Stay well-hydrated — aim for 2-3 liters of water daily
  • Manage blood pressure and blood sugar to protect kidneys
  • Avoid chronic NSAID use (ibuprofen, naproxen) which can damage kidneys
  • Moderate protein intake if kidney function is impaired (consult nephrologist)
  • Exercise regularly to maintain healthy muscle mass and cardiovascular health
  • Limit excessive creatine supplementation if monitoring creatinine levels
  • Reduce sodium intake to lower blood pressure and kidney strain
  • Avoid smoking — it accelerates kidney damage
  • Get annual kidney function screening if diabetic or hypertensive
  • Maintain a healthy weight to reduce metabolic stress on kidneys

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Historical Trend

Reference
Optimal
Last researched Feb 14, 2026

All Readings

DateValueChange
2026-01-280.9 mg/dL-0.2
2025-08-251.08 mg/dL+0.2
2025-06-270.87 mg/dL